change convergence to be before point reassignment, change point reas…

[scoutsaachi]

…signment to use updated point lengths

This is a relic from the original iteration of ticc: we used to move points before updating the cluster (which didn't do anything since we would then promptly reassign the points anyway). When we moved the empty cluster reassignment down to after the point updates, forgot to change the method to recalculate lengths.

Also, when checking for convergence, we should check before moving empty points to avoid oscillations where the algorithm has converged, but it just converged on an outcome we don't like (i.e empty clusters).